Communications over data networks has become an essential aspect of today's commercial activities and personal correspondence. One of the major hindrances to a greater acceptance of this medium is the concern over the security of personal and corporation-sensitive information carried between the inside world and the outside world. An important part of any network connected to the outside world today is a security mechanism frequently known as a firewall. A firewall has one simple function, to examine data and pass or reject it based on some established policy information. This policy could range from a very simple set of rules to one that is highly complex with thousands of rules. A firewall that is fast, tolerant to internal faults, and whose policies can be easily changed is desirable, particularly for carrier-grade services.